Cyclic 3′,5′-guanosine monophosphate (cGMP), an intracellular secondary messenger, is converted from GTP by guanylate cyclase and broken down to GMP by phosphodiesterases (PDEs), e.g., PDE 5. It plays an important role in various physiological functions. For example, it relaxes the vascular smooth muscle in organs such as heart, lung, and penis. GMP deficiency causes various disorders, e.g., coronary heart disease, hypertension, and impotence.
As cGMP is hydrolyzed by PDEs, disorders related to cGMP deficiency caused by high PDE activity can be treated by administering a PDE inhibitor to increase the cGMP levels.